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1.
H. G. Nass 《Euphytica》1979,28(1):161-167
Summary Three methods were evaluated as potential aids in identifying superior crosses early in the breeding program: (1) F1 yield, (2) F2 yield, and (3) midparental yield. Two sets of spring wheat (Triticum aestivum L. em. Thell.) crosses and parents were evaluated in replicated single row plots in F1 and in replicated multi-row plots in F2 over a period of five years. On the basis of F1 yields, two of the highest yielding and two of the lowest yielding crosses in each set were chosen for a more detailed selection study in subsequent generations.In Set 1, random F2 head selections for each of the selected four crosses were evaluated in 3-row yield plots in F4. In Set 2, F2 plant selections were made on the basis of head weight and the highest yielding 10% evaluated for yield in F4.Lines of crosses identified as high yielding in F1 had significantly greater mean yields in F4 than those of crosses that were low yielding in F1. The high yielding crosses had three to four times as many lines yielding in the top 10% in F4 than did the low yielding crosses.Correlations for yield were obtained between F1 and F2 in different years, F2 and midparents in the same year, lower or no correlations between F1 and midparents in the same year, and no correlations between F1 and midparent and F2 and midparent in different years. It is suggested that larger plot sizes rather than single rows be used to evaluate parents.Midparental yield, F1 yield and F2 yield tests are recommended as a progressive set of screening tests for a given set of crosses to effectively maintain the superior crosses in the breeding program. 相似文献
2.
Genetic response to index selection for grain yield, kernel weight and per cent protein in four wheat crosses 总被引：1，自引：0，他引：1
Quantitative genetic theory was used to investigate selection differentials, expected and observed direct and correlated responses to simultaneous improvement of grain yield, kernel weight, and grain protein content in F3 and F4 populations of four spring wheat (Triticum aestivum L.) crosses. Selection in the F3 generation based on the Smith-Hazel index (SH) and yield was found to be superior to the other methods studied in identifying high-yielding lines, but resulted in substantial decrease in grain protein level. Consequently, a 1.0% increase in protein from selection for protein depressed grain yield as much as 536 kg/ha below the population mean, reducing the expected yield gains per generation selection cycle by 250%. The weight-free indices (EW), particularly the index involving only yield and kernel weight (EW3) and its linear approximation (EW4), and the desired gains indices were effective in improving protein content but were less efficient in selecting top-yielding lines. Selection in the opposite direction using truncation of the lowest 10% of the population based on weight-free-index involving yield, kernel weight and protein (EW2) reduced all traits significantly compared with the mean of the unselected population indicating the effectiveness of the unweighted selection index. The observed genetic gains (Ra) from selection based on yield, the SH, EW3 and EW4 indices were slightly lower than the expected advances per cycle (R) in populations from crosses ‘Sinton’בGlenlea’ (C1), ‘Glenlea’בNB505’ (C2), and ‘A2P5’בNB320’ (C6) (Ra/R = 70 to 85%) but were higher in cross ‘NB505’בA2P5’ (C5) (Ra/R = 126 to 143%). It was concluded that weight-free and the desired gains indices can be used to improve wheat grain yield and grain protein simultaneously in F3 generation selection, as revealed by response to selection measured in the F4 generation. 相似文献
3.
Summary Aspects of selection for yield and harvest index were investigated by simulating selection using data from random pedigreed F2, F3, F4 and F5 derived lines from two crosses grown in plots at two sites over two years.Improvement in yield through selection was obtained when the response was measured at the same site and in the same year as the selection. Selecting the best 10 per cent of F2 to F4 derived lines gave F5 derived lines that outyielded random selections by 19 to 53 per cent for one cross and 5 to 23 per cent for the second cross. These lines were 41 to 50 per cent better than the mid-parent in one cross, but were less than the mid-parent in the other cross.However, the response to selection when measured in a different year was little better than random selection. The effect of different sites also reduced the effectiveness of selection.Selection of harvest index in early generations for improvement of yield was ineffective when response was measured at the same site in the same year, or in different years.Contrary to some theoretical proposals, the same improvement in yield was obtained by selecting in early or late generations. While high yielding genotypes may be lost by delaying selection, this is counteracted by the better predictive value of late generations due to their greater homozygosity and homogeneity. 相似文献
4.
D. Roupakias A. Zesopoulou S. Kazolea G. Dalkalitses A. Mavromatis T. Lazaridou 《Euphytica》1997,93(1):63-70
The effectiveness of early generation selection under low and high plant density was evaluated in faba bean (Vicia faba L.). For this, the faba bean cv. 'Polycarpe' was pollinated by eight higher yielding cultivars of different origin. The F1's and F2's together with 'Polycarpe' and the pollinator with the highest yielding ability (cv. 'Effe') were evaluated under high plant density with adjacent controls and under low plant density in a honeycomb design. It was found that the eight hybrids had a different ranking at low than at high plant density for both generations (F1and F2). Hybrid Pol.x A-58 had the best combined yield performance in the F1and F2under high and hybrid Pol.x A-37 under low plant density. Application of individual plant selection in the F2and F3generation of the two crosses (Pol.x A-58 and Pol.x A-37), under both low plant density according to UNR-O honeycomb design and high plant density using a moving average, resulted in the selection of four groups with 20 selected F3plants each. Within each group, equal numbers of seeds from each plant were mixed to establish four mixtures. These mixtures together with two controls ('Polycarpe' and 'Effe') were evaluated in a randomized complete block design (22 plants/m2) in one location for two years. It was found that the material selected continuously under low plant density had a significantly higher yield than the material selected under high plant density. In addition, the material selected from Pol.x A-37 (H1R2) under high plant density had a lower mean yield than that selected continuously under low plant density (H1H2). Their average yield over years was significantly higher than the yield of the material selected from Pol.x A-58 under both plant densities. Furthermore, the material selected from Pol.x A-58 under low plant density, had a significantly higher mean yield over years than its sibs selected under high plant density. It was concluded that honeycomb selection at low plant density can be used effectively for early generation selection in faba bean. 相似文献
5.
Summary Significant advances in increasing tolerance to the leafhopper Empoasca kraemeri Ross & Moore in common bean have been obtained using a new breeding scheme where yield under leafhopper attack is the principal selection criterion in the evaluation of progenies. However, to further refine this breeding scheme, a study was conducted to determine whether selection for nonprotected yield would be more effective in early versus late generations. Two selection strategies were compared. In Strategy I, early generation selections in the F2 and F3 were compared to Strategy II where late generation selections were made in the F4 and F5, with the F2 and F3 generations advanced using single pod descent and bulk practices, respectively. Yield trials of the F6 lines from both selection strategies were conducted under nonprotected and insecticide protected treatments. No significant differences were detected between the two selection strategies. However, Strategy II did produce advanced lines with greater nonprotected yields than did Strategy I, with the best F6 line, in three out of four crosses, coming out of Strategy II. Late generation selection is recommended over early generation selection. Results of the new leafhopper breeding scheme, based on yield, are compared to the old breeding scheme where selections were made using visual selection practices in early generations. 相似文献
6.
Summary Stem solidness in the wheat plant provides resistance to the wheat stem sawfly, a pest of wheat in Montana and North Dakota, but some agronomists have been concerned that stem solidness might be related to low grain yields. We evaluated 17 spring wheat crosses for stem solidness, grain yield, and other agronomic traits in F2 through F4 generations from 1972 to 1975.Highly significant correlation (0.735) and regression (0.731) coefficients between F2 and F3 generations verify previous studies showing that stem solidness is highly heritable and that selection in F2 should be successful. Solid-stemmed F4 composites yielded more than hollow stemmed composites at Bozeman and equal yields were obtained at Huntley, indicating that stem solidness is not a deterrent to high grain yield.Joint contribution of Federal Research, Science and Education Administration, U.S. Department of Agriculture and the Montana Agricultural Experiment Station, Bozeman, MT 59717. Published with approval of the Director of the Montana Agricultural Experiment Station as Paper No. 815, Journal Series. 相似文献
7.
A. J. van Oeveren 《Euphytica》1992,64(1-2):91-97
Summary Two selection procedures in wheat breeding were compared on the basis of their ability to supply high yielding inbred lines. The first procedure consists of an early selection between crosses in the F3 generation, based on cross performance. In the second procedure selection is postponed until the F6, which is derived by single seed descent. The two procedures are evaluated in a two year test, using pseudo-lines of spring wheat. These pseudo-lines consist of mixtures of varieties and enable an estimation of the true genetic parameters. In this way the accuracy of the predictions can be examined.The first year of this comparison comprised the actual selection process and in the second year an F6 and F7 generation were mimicked, based on the selected lines of the F3 and F6 respectively, and evaluated in a large yield test. This paper gives the final results after the second year. From the first year it was found that the F3 cross predictions were very inaccurate, whereas selection in the SSD-F6 appeared to perform well. This resulted in a higher yielding set of lines evolving from the SSD-F6. Despite a pronounced genotype-year interaction this difference in yield level was also found between the F7 and the F6 lines, derived from the selected crosses in the F3. We conclude that the early selection procedure is not advantageous compared to the fast SSD procedure. 相似文献
8.
Selection for yield in early generations is difficult, mainly due to a shortage of seed. In the breeding company Fr. Strube the breeder uses three-way crosses and first selects for yield between F2′-derived lines in the F4′. The generations are called F1, F2′, etc., because the first generation is already segregating. The efficiency of this selection was checked in the F5′ and F6′. For this purpose F3′-derived progenies, corresponding to poor and good yielding bulks in F4′, were selected. In later generations the average yield of the group of strains with good yield in the F4′ was 4 % (F5′) and 3 % (F6′) higher, respectively, than the mean of the strains with low yield in the F4′. Strains with very low yielding potential can easily be discarded in the F4′. The risk of discarding lines with a very high yield is minimal. Selection for yield in the F4′ was as effective as in the F5′. The importance of testing F2′-derived bulks in the F4′ is not only based on the assessment of yield but also on the possibility of reliable intensive selection through recording visual characters (height, resistance against diseases) in a second environment in parallel to the single plant progenies. 相似文献
9.
Summary The efficiency of indirect selection for seed yield was compared with direct selection for yield per se in chickpea. A total of 2500 single F2 plants, derived from 50 crosses with 50 plants from each cross, were divided into five sub-populations (SP1 to SP5) of 500 plants each by including 10 plants from each of the 50 crosses. The five sub-populations were advanced upto F6 by exercising 10% selection intensity for four successive generations for number of pods per plant in SP1, number of seeds per pod in SP2, seed weight in SP3, seed yield in SP4 and random selection in SP5. The efficiency of direct and indirect selection for yield was evaluated by comparing groups of 50 F6 lines from each sub-population. SP1 and SP3 F6 lines showed higher mean grain yield than the other three methods. SP1 and SP3 were found to be almost equally efficient in developing F6 lines which were significantly superior to the check. This suggests that indirect selection for yield via pod number and seed weight is more efficient than direct selection for yield. 相似文献
10.
Selection for biomass yield in wheat 总被引：2，自引：0，他引：2
R. C. Sharma 《Euphytica》1993,70(1-2):35-42
Summary Biomass (above ground plant parts) yield may be a useful selection trait for yield improvement in wheat (Triticum aestivum L.). This study was conducted to estimate realized heritability of biomass yield and to determine the response to selection for high and low biomass yield in 8 genetically diverse populations of spring wheat under two production systems. Selections were made among the F3 lines. Progenies of the selected lines were evaluated in replicated field tests in the F4 generation under high fertility and low fertility production systems at Rampur, Nepal, in 1991. Fertility level had a significant effect on biomass yield, grain yield, effective tiller number, number of kernels per spike, thousand kernel weight, and harvest index. Selection in the F3 for high and low biomass yield was effective in identifying F4 lines with high and low biomass yield, respectively. Biomass yield differences between high and low selection groups in the F4 generation, expressed as percent of the mean of the low selection group and averaged over the eight populations, were 53.9 and 36.5% higher than the mean of the low selection group under the high and the low fertility production systems, respectively. The corresponding figures for grain yield were 48.8 and 34.9% under the high and the low production systems, respectively. Also, selection for high biomass yield resulted in higher effective tiller number, and number of kernels per spike, but lower harvest index. Realized heritability estimates for biomass yield were greater at high fertility (range 0.49 to 0.85) than at low fertility (range 0.22 to 0.44). Biomass yield showed positive genotypic correlations with grain yield, effective tiller number, and number of kernels per spike but a negative correlation with harvest index. The results indicated that selection for high biomass yield should bring about positive improvements in biomass yield, grain yield, effective tiller number, and number of kernels per spike. The correlation between F3 and F4 generations suggested that biomass yield in the F3 generation was a good predictor of biomass yield and grain yield in the F4 generation. Selection for biomass yield in wheat should be made under the standard production system to obtain a realistic response. 相似文献
11.
Summary Two breeding procedures were compared in two cowpea crosses. Both procedures were started from the same selected F2 plants in each cross. For the early generation yield testing, the F3 lines were yield tested and a pedigree and bulk methods followed in F4 and F5. Each F5 line was bulked to provide seed for a yield test in F6. In the Single Seed Descent (SSD) procedure, a single seed was taken from each F2 plant to produce the F3 generation. The procedure was repeated for the F4 and F5. The F6 SSD lines and the F6 yield testing lines were compared in yield tests.The results showed that differences in yielding ability of F3 lines persisted over generations indicating that selection was effective. This was confirmed by the high significant correlations between F3 yields and those of later generations which ranged from r=0.51* to 0.85**.The grain yields of lines derived by the single seed descent procedure were as good as those derived from early generation yield testing.Significant linear correlation between visual rating of F3 and F6 yields with actual yields revealed that it is possible to identify promising lines of cowpea visually. 相似文献
12.
F2 populations derived from a half diallel cross between 11 spring bread wheat cultivars were classified according to segregation
for heading date in a spring environment. Seventeen populations segregated very late plants, presumably of winter type, resulting
from the presence of different Vrn genes in the parents. The objective of the study was to evaluate the performance of these
spring x spring crosses grown in a winter wheat environment. F2 plants were selected from six populations and were simultaneously exposed for several generations to the winter wheat environment
(Toluca, Mexico, winter) and spring wheat environment (Ciudad Obregon, Mexico, winter; Toluca, spring). Visual selection was
conducted on F3-F5 populations for agronomic type relevant to the environment under which the segregating generations were grown. The lines
grown in the spring environment performed very well and a number of them were promoted to advanced generation testing. The
same lines grown in the winter environment suffered from frost and were almost entirely discarded, proving that spring × spring
crosses have limited value for germplasm improvement targeted for conditions similar to the Toluca highland winter environment.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
Relationship between relative water content during reproductive development and winter wheat grain yield 总被引：2，自引：0，他引：2
Summary Water is often the most limiting factor to winter wheat (Triticum aestivum L.) production in the southern Great Plains of the U.S.A., yet the lack of reliable screening criteria has precluded direct selection for drought resistance in breeding programs. Previous work showed that leaf relative water content (RWC) was highly heritable when measured under field-drought conditions, but its adoption as a screening tool for yield improvement requires further investigation of the genetic relationship between grain yield and RWC. Plants representing high and low yield potential under drought stress, and a random group of plants, were selected from an F2 population having the pedigree, TAM W-101/Sturdy. Two sets of entries, each comprised of the two parents and 24 F2-derived lines, were evaluated under a rainshelter in the F3 (1986) and F4 (1987) generations to determine differences in leaf RWC during reproductive development. One set of entries did not receive any water after the jointing stage, and the other set was grown under well-watered conditions. A positive relationship was observed between grain yield and RWC measured during anthesis and mid-grain fill, as the high-yield selections maintained a significantly higher RWC than the low-yield selections. Grain yield and RWC were also positively associated among random selections segregating for both traits. Subsequent adjustment of genotype means for differences in reproductive development at time of sampling underscored the need to consider differences in maturity when RWC is the selection criterion. 相似文献
14.
Summary Gene action and heritability of groat protein percentage were determined in F1, F2, and F3 generations of nine crosses between three Avena sativa L. cultivars and three A. fatua L. selections. Relationships among groat protein percentage, grain yield, and 100-seed weight also were evaluated. The three A. sativa parents were Dal (high grain yield and intermediate groat protein percentage), Goodland (low grain yield and high groat protein percentage), and Stout (high grain yield and low groat protein percentage). The three A. fatua parents were chosen for the study on the basis of vigorous plant growth and high groat protein percentage. The study was conducted at Madison, Wisconsin in 1979 and 1980.There was partial dominance towards low groat protein percentage. Narrow sense heritability estimates for groat protein percentage were low in Dal and Goodland crosses and intermediate in Stout crosses. In the F2 generation, groat protein percentage was significantly higher in shattering than in nonshattering plants in 1979, but not in 1980. There were significant, positive correlations between groat protein percentage, 100-seed weight, and grain yield in F1 and F2 generations, but they were not large numerically. Relationships among these traits were either negative or nonsignificant in the F3 generation. Although our results indicated that selection for higher groat protein percentage is possible when a low protein A. sativa cultivar is used, most of our simple cross progenies from A. sativa x A. fatua crosses had weak straw and were susceptible to crown rust (Puccinia coronata
Cda. var. avenae
Fraser and Led.). 相似文献
15.
Summary Five parents from each of four race groups of common bean (Phaseolus vulgaris L.) were hybridized to produce five crosses within each group. Also, five crosses were made for each of the six possible combinations among four groups. Parents, F1 and F2, and parents, F2 and F3 were evaluated for seed yield in 1990 and 1991, respecitively, at two locations in Colombia.Yield of parents belonging to Middle American races and crosses among them was higher than that of races of Andean origin. Positive correlations were found among the mid-parent value, F1, F2 and F3. Also, the mid-parent value predicted the mean seed yield of all possible lines that could be derived from the F-generation in 42 out of 47 crosses. Four crosses, all between common bean races of Andean and Middle American origin, indicated a possible loss of favorable epistatic parental alleles. On average, mean yield of interracial F1 hybrids was higher than that of intraracial ones.Positive heteroris (26.4%–123.8%) over the mid-parent in 31 crosses, and F1s yielding higher (23.7%–91.8%) than the high parent in 20 crosses and yielding higher (22.1%–53.2%) than the highest control among all parents (MAM 13) in 12 crosses, were found. Heritability, estimated by the parent-offspring regression, ranged from 0.42± 0.07 to 0.49±0.04. Expected and realized gains from selection (at 20% selection pressure) ranged from 10.3% to 21.0% over the mean of F1 hybrids and F2 and F3 population bulks. 相似文献
16.
Earlier studies showed that the ratio of the weight of the wheat ear to stem at anthesis (ear:stem ratio) may give a better indication of potential yield than harvest index because it is determined early in the life cycle and is not affected by post anthesis stress. These studies concluded that selection for high ear:stem ratio at anthesis may lead to further improvement in grain yield of wheat. The present work was undertaken in the field to identify lines varying in ear:stem ratio in breeding populations and to study its implications for yield improvement.At anthesis stem length, ear length, tiller number, dry weight of stem and ear and ear:stem ratio were measured in 14 crosses on F2 single plants and F2 derived lines grown in the F3, F4, and F5 at three locations in Western Australia over four seasons. In addition, biomass, grain yield and yield components were measured on selected crosses at two locations on F2 derived lines grown in the F4 and F5. There was a considerable range of ear:stem ratio between and within the crosses studied. Although ear:stem ratio was strongly correlated with stem length, there was substantial variation within stem length classes. Ear:stem ratio had a high mean broad sense heritability (82%), whereas HI, grain yield and above ground biomass had lower heritabilities, 68, 55 and 35% respectively. Ear:stem ratio was strongly correlated between generations and sites indicating stability of this character. Ear:stem ratio had a significant positive correlation with grain yield, HI, grains per ear and per m2. The correlation of grain yield with HI was equal or slightly higher than that of grain yield with ear:stem ratio.Ear:stem ratio offers promise as a predictor of HI and yield potential where post-anthesis moisture stress can influence HI. Ear:stem ratio measurement is unlikely to be adopted for selection purposes in routine breeding programs, as it is laborious and time consuming. However, ear:stem ratio could be used to identify superior parental genotypes and early generation selections from special crosses in terms of its ability to partition assimilate. 相似文献
17.
M. Santalla M. Lema A. P. Rodiño A. M. González A. B. Monteagudo A. M. De Ron 《Euphytica》2005,142(1-2):85-95
Approaches are needed to broaden the genetic base and improve earliness and yield potential of large-seeded beans under sustainable cropping systems. The objective of this research was to develop adapted dwarf bean populations having a commercial seed quality and yield suitable for the production in the South of Europe. The original base populations were produced from crosses between genotypes within each Mesoamerica, Nueva Granada and Peru races, and between Peru and Nueva Granada, and Mesoamerica and Nueva Granada races. Visual mass selection for plant performance was practised in the F2 and F3 generations. In the F4 and F5, single plants were harvested under two cropping systems (sole cropping and intercropping with maize). From F4, selection was based on precocity, combined with seed yield and seed commercial type. The F4:7 selected lines from each original population were compared with their parents and five checks at four environments and two cropping systems. Differences among environments, populations, parents and checks were observed for all traits. Under intercropping with maize, there was a 50% reduction in seed yield. Yield of parents and checks belonging to Andean South American races, intraracial (Nueva Granada × Nueva Granada) and interracial (Nueva Granada × Peru) populations, was higher than that of those of Middle American origin. Intraracial crosses within large-seeded Andean South American (Peru race) and Middle American gene pools (Mesoamerica race) did not produce lines yielding more than the highest yielding parent. Only two large-seeded lines selected from crosses between small- and large-seeded gene pools out-yielded the best parent and check cultivar. 相似文献
18.
Seed production in peas is limited by early and severe lodging and by a low multiplication rate and pea breeders have tried to overcome such disadvantages by growing plants in early generations widely-spaced against wire netting. Progenies of four pea crosses were each tested over a period of tour years to investigate whether single plant selection for quantitative characters, in particular grain yield, is efficient in such circumstances in the Is generation. Efficiency of selection was also studied for yield and yield related characters in the F3 based on f2 derived single plant progenies grown in unreplicated microplots. Early yield selection in the F2 as well as in the F3 proved to be of poor efficiency. Heritability values of all recorded traits were only slightly higher in the F3 than in the F2. Efficiency of yield selection could not be increased significantly in these early generations by indirect selection, either for single traits or for index traits. Possible reasons are discussed for the low efficiency of direct and indirect selection for grain yield in early generations and proposals are made for its improvement and for alternative selection strategies. 相似文献
19.
Summary The relationships between yield, its components and other associated characteristics, both within and across generations, were studied in the F2, F3 and F4 of two Hard Red Spring wheat (Triticum aestivum) crosses using simple correlation, path coefficient and step-wise multiple regression analyses. In the F2 and F3 the plants were grown 50 cm apart from each other while in the F4 they were grown under the usual farm practices. Selection was practiced for high and low yield in the F2 and F3 mainly on the basis of individual plant yield. Statistically significant, but not always practically useful, correlations were found between yield and its components and other associated characters. The relationship between yield and protein content was negative and significant within all generations but not so between F2 (and F3) and F4. The intergeneration correlation coefficients between F4 grain yields and grain yields measured in the F2 and F3 were all positive and highly significant. These coefficients, which are also heritability estimates in standard units, were small in magnitude.Stepwise multiple regression analysis identified plant yield as the most significant factor in determining F4 line yield, followed by its components in the order of 1000-kernel weight, grain yield per plant and number of tillers per plant.Path coefficient analysis identified tiller number per plant and grain yield per spike as having strong positive direct effects on single plant yield. Harvest index of individual F2 plants can be used as an indirect selection criterion for yield. 相似文献
20.
Crosses were made between two widely grown U.S. peanut (Arachis hypogaea L.) cultivars, ‘Florunner’ and Florigiant’, and two genotypes adapted to growing conditions on the plateau of tropical Africa, ‘Makulu Red’ and 486 GKP. F2 seed populations were equally divided between Georgia and Zimbabwe. Subsequently, pedigree selection was practised simultaneously at both locations in the early segregating generations. The highest yielding pureline selections were then interchanged, and combined yield evaluations were determined over three growing seasons at each location. ‘Florunner’, ‘Florigiant’, and the Georgia pureline selections tested at the Georgia location had significantly higher pod yields than ‘Makulu Red’, 486 GKP, and the Zimbabwe selections. Conversely, the mean yield of the Zimbabwe selections tested m Zimbabwe was significantly higher than that of the Georgia selections. Thus, the breeding environment under which selection is conducted among cross populations strongly influences the yield adaptability of selected peanut genotypes. 相似文献